Hi Vijay,
YEs, reconfirming what others have said Ex2013 CALs covers Ex2010 CALs. Here are some references confirming the same. Please go through to understand more.
Please note that, if you are in doubt, don't use it and consult a licensing vendor\consultant.
https://www.directionsonmicrosoft.com/licensing/2012/12/downgrades-are-key-license-compliance
Many server productssuch as Windows Server and Exchange Serverrequire a CAL for each client user or device. CALs license a client's access to all instances of the server product running within the organization, and the version of the CAL must match or
exceed the version of the server software the client encounters.
A common noncompliant scenario of this type is a customer who purchased Office Professional Plus licenses but deployed Office Standard. Although somewhat counterintuitive, Office Professional Plus licenses do not include edition downgrade rights to Office
Standard.
They are limited to the same functional editions within each version (for example, Windows 10 Enterprise downgrades to Windows 8/8.1 Enterprise or Windows 7 Enterprise; however,
Windows 10 Pro doesnt downgrade to Windows 8/8.1 Enterprise or Windows 7 Enterprise).
Version downgrade rights across most of Microsoft products are discussed in the "Downgrade rights for Microsoft Volume Licensing, OEM, and full-package product licenses" licensing brief at
www.microsoft.com/licensing/about-licensing/briefs/downgrade-rights.aspx.
Fulfillment information:Access to prior product versions July 2015 update
http://www.microsoft.com/en-us/licensing/existing-customer/fulfillment.aspx